"See that little stream? We could walk to it in two minutes. It took the British a month to walk to it  a whole empire walking very slowly, dying in front and pushing forward behind."

 F. Scott Fitzgerald,
"Tender Is the Night"

The walk began at 7:30 a.m., July 1, 1916 , when British infantry advanced toward German trenches. In the first hours, eight British soldiers fell per second. By nightfall, 19,240 were dead, 38,230 more were wounded. World War I, the worst man-made disaster in human experience, was the hinge of modern history. The war was the incubator of Communist Russia, Nazi Germany, World War II and innumerable cultural consequences. The hinge of this war was the battle named for "that little stream," the river Somme.

The scything fire of machine guns could not be nullified even by falling curtains of metal from creeping artillery barrages that moved in advance of infantry. Geoff Dyer, in "The Missing of the Somme," notes: "By the time of the great battles of attrition of 1916-17 mass graves were dug in advance of major offenses. Singing columns of soldiers fell grimly silent as they marched by these gaping pits en route to the front-line trenches."

William Philpott's judicious assessment in "Three Armies on the Somme: The First Battle of the Twentieth Century" is that the Somme was "the cradle of modern combat," proving that industrial war could be won only by protracted attrition.

And hence by the new science of logistics. The 31 trains a day required to supply the British at the Somme became 70 when the offensive began. The romance of chivalric warfare died at the Somme, which was what the Germans called Materialschlacht, a battle of materials more than men. Geographic objectives  land seized  mattered less than the slow exhaustion of a nation's material and human resources, civilians as well as soldiers.

In the next world war, the distinction between the front lines and the home front would be erased. In 1918, Randolph Bourne, witnessing the mass mobilization of society, including its thoughts, distilled into seven words the essence of the 20th century: "War is the health of the state." Relations among government, the economy and the individual were forever altered, to the advantage of government.

Military necessity is the most prolific mother of invention, and World War I was, Philpott writes, "a war of invention," pitting "scientific-industrial complexes" against each other: "Gas, flame-throwers, grenade-launchers, sub-machine guns, trench mortars and cannon, fighter and bomber aircraft, tanks and self-propelled artillery all made their battlefield debuts between 1914 and 1918."

Attritional war had begun in earnest at Verdun, which occupies in France's memory a place comparable to that of the Somme in British memory. And the Somme offensive was begun in part to reduce pressure on Verdun and to demonstrate that Britain was bearing its share of the war's burden.

In December 1915, Winston Churchill, then 41, said, "In this war the tendencies are far more important than the episodes. Without winning any sensational victories we may win this war." The war itself may have been begun by a concatenation of blunders, but once begun it was worth winning, and the Somme, this "linear siege" (Philpott), set the tendency for that. Germany, trying to slow the transatlantic flow of materiel, resorted to unrestricted submarine warfare, which, five months after the Somme ended, brought the United States into the war and, in a sense, into the world.

Thomas Hardy's description of the 1813 Battle of Leipzig  "a miles-wide pant of pain"  fit the Battle of the Somme, where a soldier wrote, "From No Man's Land . . . comes one great groan." The Somme ended on Nov. 18, with men drowning in glutinous lakes of clinging mud sometimes five feet deep. This was the war that British poet Rupert Brooke had welcomed as G0D's gift to youth awakened from sleeping, "as swimmers into cleanness leaping." By November a million men on both sides were dead  72,000 British and Commonwealth bodies were never recovered  or wounded. Twenty-two miles of front had been moved six miles.

But because of this battle, which broke Germany's brittle confidence, the war's outcome was discernible. Not so its reverberations, one of which was an Austrian corporal whose Bavarian unit deployed to the Somme on Oct. 2. Adolf Hitler was wounded on his third day in the line.

The Battle of the Somme is, in Dyer's words, "deeply buried in its own aftermath." As is Europe, still.